thermostatic turns cold after 3mins

[drainrod]

having nice hot shower then water turns cold for couple mins then hot again, cycle continues
wb 35cdi 9yr old, BUT when heating not on shower runs nice and hot and doesnt change
answers please

 

[Scott_D]

does it happen at other hot outlets?

 

[Aire]

What you need to establish is whether the boiler is cutting out when this happens. Run your shower as you normally would, but then go to your boiler and monitor how it functions. If the boiler cuts out then it's an issue within your boiler. If the boiler runs continually then the fault will be within the shower control.

 

[SimonG]

Drop shower off and check filters in addition to what Craig said above.